1. Field of the Invention
The invention concerns an input circuit for an integrated HF-transmitting component of a battery-operated device for the transmission of a data signal, wherein a reference oscillator is connected to one of the inputs of the transmitting component.
2. Discussion of the Prior Art
Battery-operated devices of that kind are, for example, consumption measuring devices which cyclically transmit radio signals corresponding to the respective consumption status in order to be able to detect the consumption status for consumption billing from outside the building or room in which the consumption is taking place. Such consumption measuring devices can serve for a determination of the water consumption measured by means of a water meter, or for the heat consumption of heating devices or power consumption. The consumption measuring devices should consist of a small compact structure, and are to be maintenance-free over a period of several years. For example, radio frequencies of 433 MHz, 868 MHz and 915 MHz (USA) are provided for the operation of such devices.
The ASK/FSK-transmitter 868/433 MHz TDA5100 or TDA5102 (USA-version) or the TDA51xx family from Infineon Technologys AG are known as an inexpensive HF-transmitting component. Similar components are also known as being available from other manufacturers. With the usual connection of the transmitting component to a reference oscillator the data rate which can be transmitted is limited to about 20 kchip/s; which represents a drawback. This is because, the lower the data rate is, the correspondingly longer the data telegrams become, and correspondingly greater because the current consumption during the transmission of the data telegrams. A high level of power consumption is inexpedient because the battery-operated device is intended to operate for years without the batteries having to be replaced or re-charged.